In coronary artery disease the supply of oxygen rich blood to part(s) of the heart muscle may be partly choked or even totally choked by a narrowing, e.g. stenosis, of one or several coronary arteries. The effect of choked blood flow to the heart spans from pain in the chest (i.e. angina pectoris), to ischemia eventually causing heart failure and possible death.
Historically, it has been thought that detection and quantification of arterial narrowings may be performed by X-Ray angiography alone.
In X-Ray angiography, an image representation of the arteries is obtained after injection of a contrast agent. However, X-Ray angiography is presently not commonly used alone for diagnosing the severity of stenosis. Rather, X-Ray angiography is combined with an intravascular measurement of the pressure and/or blood flow, or combined with intravascular ultrasound.
Intravascular measurements of the pressure and/or blood flow may be performed by use of guide-wire with sensor(s) at the distal end. Typically, the guide-wire with the sensor(s) is inserted into the body via vessels in the groin. The guide-wire, with sensor(s), is normally operatively connected to a control unit receiving input data from the sensor(s). By connecting the control unit to a display unit the pressure may be observed in real time.
Fractional Flow Reserve (FFR) is a ratio which relates to the pressure differences across a coronary artery stenosis (narrowing, usually due to atherosclerosis). From the FFR measured, the likelihood that the stenosis impedes oxygen delivery to the heart muscle, eventually causing myocardial ischemia, may be determined FFR is defined as the pressure behind (distal to) a stenosis relative to the pressure before the stenosis and does thus also relate to the pressure drop over the stenosis. FFR is an absolute number and an FFR of 0.50 is seen if the pressure drop over the stenosis is 50%. Thus, FFR is a comparison of the maximal blood flow in the vessel in the presence of a stenosis compared to the maximal blood flow in the hypothetical absence of the stenosis. Typically, also FFR may be measured by use of guide-wire with sensor(s) at the distal end.
Intravascular ultrasound (IVUS) is a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter. The proximal end of the catheter is attached to a computerized ultrasound equipment generating an ultrasound image. By use of IVUS it is possible to “see” from inside blood vessels out through the surrounding blood column, visualizing the endothelium (inner wall) of blood vessels in living individuals.
The arteries of the heart (the coronary arteries) are the most frequent imaging target for IVUS. IVUS may for example be used in the coronary arteries to determine the amount of atheromatous plaque built up at any particular point in the epicardial coronary artery. It is also used to assess the effects of treatment of stenosis, such as with hydraulic angioplasty expansion of the artery, with or without stents, and the results of medical therapy over time.
X-ray angiography imaging is used within the art to monitor the position of an intravascular probe used for measuring of a hemodynamic parameter or for generating an IVUS signal within a blood vessel. An examining physician typically relies on the X-ray angiography imaging to monitor the position for probe used for measuring of a hemodynamic parameter or for generating an IVUS signal; whereby the location of e.g. stenosis of coronary artery may be determined. Hence, intravascular measurements guided by X-ray angiography imaging are useful in diagnosing cardiovascular diseases.
In the art, X-ray angiography imaging data is visualized in real time, separately from the real time representation of an intra vascular hemodynamic parameter, such as the intravascular pressure or flow, or the intravascular ultrasound (IVUS) imaging signal. In order to assist the physician, it would be of value to avoid having to look at separate screens.
The prevalence of cardiovascular disease is rapidly increasing, especially in the western parts of the world. So are the costs for health care. The possibility to scrutinize a diagnosis, or for the examining physician to justify it, afterwards is therefore growing more and more important. There is therefore also a need for a reliable and efficient way of archiving examinations results in the art.